1. Field of the Invention
This invention relates to confidential information protection of an electronic document such as data in an electronic form, and also to usage rights management to read, view, and edit the electronic document and the like.
2. Description of the Related Art
In recent years, more and more business enterprises and the like are making active efforts to protect confidential information. More particularly, attention is currently focused on confidential information protection technology that prohibits third parties from reading and viewing a confidential document by encrypting a document and controlling the distribution of an encryption key.
Related art 1. Digital copyright management technology is a first possible related art applicable in order to implement the confidential information protection. However, the digital copyright management technology is designed to protect copyright in literary work and Detail Code. It is, therefore, only expected to quote information in protected documents without changing the contents. This means that the objective or idea of the digital copyright management technology is different from that of the confidential information protection. Accordingly, there is no way for the current digital copyright management technology to prohibit access to read protected documents.
Related art 2. Another possible conventional technology for confidential information protection, which is labeled Patent Document 1 below, has been proposed. Patent Document 1, entitled “System and method for distributing digital works, apparatus and method for reproducing digital woks, and recording medium”, is configured with an editing apparatus to edit and encrypt document data, a ticket server apparatus for managing and distributing an encryption key and usage rights, and an audiovisual apparatus for reading and viewing a document. The audiovisual apparatus is allowed to decode and display the document data only when receiving the right ticket distributed. Then, the audiovisual apparatus, when receiving editing rights, is allowed to send decoded document data to the editing apparatus. The editing apparatus edits the document data to generate a new encrypted document, and sends the encryption key and usage rights to be registered in the ticket server apparatus.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-48076